The Ministry for the Environment's latest report card - issued weeks before summer weather sends Kiwis flocking to the water - has left opposition parties questioning New Zealand's 100 per cent pure brand.

The results showed water quality was poor or very poor at 52 per cent of monitored river sites.

A further 28 per cent were graded "fair" - with a risk of illness for those swimming there.

Only 20 per cent of monitored river recreation sites were graded good or very good.

Beaches did better, with 60% rated as "good" or "very good". But its still an appalling indictment on our environmental record, and on the government which has allowed this deterioration to happen. And it naturally damages our tourism, as well as our health.

As for the cause, the fact that the problem is with rivers and not beaches points the finger firmly at farmers. They're destroying the country - and our tourism industry - for their own profits, externalising their costs in the form of pollution. Its long past time they were forced to clean their act up.